a. Field of the Invention
The instant invention is directed toward an electrode for a catheter, including an electrode that may simultaneously emit electrical energy and facilitate visualization by magnetic resonance imaging (MRI).
b. Background Art
Catheters have been in use for medical procedures for many years. Catheters can be used for medical procedures to examine, diagnose, and treat while positioned at a specific location within a body that is otherwise inaccessible without more invasive procedures. During these procedures a catheter is commonly inserted into a vessel near the surface of the body and is guided to a specific location within the body for examination, diagnosis, and/or treatment. For example, one procedure often referred to as “catheter ablation” utilizes a catheter to convey an electrical stimulus to a selected location within the human body to create tissue necrosis. Another procedure often referred to as “mapping” utilizes a catheter with sensing electrodes to monitor various forms of electrical activity in the human body.
Catheters are also used for medical procedures involving the human heart. Typically, the catheter is inserted in an artery or vein in the leg, neck, or arm of the patient and directed, sometimes with the aid of a guide wire or introducer, through the vessels until an electrode of the catheter reaches the desired location for the medical procedure in the heart.
Conventional ablation procedures utilize a single distal electrode secured to the tip of an ablation catheter. Increasingly, however, cardiac ablation procedures utilize multiple electrodes affixed to the catheter body. These ablation catheters often contain a distal tip electrode and a plurality of ring electrodes. Mapping catheters also often contain a plurality of sensing electrodes to monitor various forms of electrical activity in the human body.
An application may be utilized to create images of the catheter's surroundings. Images may be acquired through visible light, ultrasound, or magnetic resonance (MR). The application may be used to acquire high resolution radiographic images of tissue surrounding the catheter, for example, the acquisition of high resolution magnetic resonance images of blood vessel walls for the visualization and differentiation of various types of tissues and plaques.
Magnetic resonance imaging (MRI) may also be employed during a medical procedure to assist a physician in guiding a catheter and/or a portion of a catheter, such as an electrode. For example, tracking devices may be attached to a catheter (or other medical device) to be tracked. The tracking device may comprise a coil (e.g., induction coil). An MR pulse sequence may be performed where the coil is used to acquire a signal which indicates the location of the tracked device (e.g., catheter). The location of the coil may be determined and superimposed at the corresponding location in a medical image acquired with an MR imaging system.
Conventional designs for catheters for MRI-guided electrode positioning may rely on a plurality of tracking devices placed at discrete locations along the longitudinal axis of the catheter shaft. The tracking devices may be located on the shaft proximal to an electrode. The tracking devices may be utilized to sense and indicate the location and orientation of the catheter within a body through a control system. The control system may also be used to control a set of imaging coils to image selective areas of the body cavity and/or to control the amount of energy applied to electrodes (e.g., ablation elements) on the catheter to treat target tissue. The energy may cause heating, and at certain temperatures, tissue cells may be destroyed. A plurality of tracking devices may be required in order to provide information regarding the flex of the catheter shaft. Conventional designs may utilize a plurality of tracking devices on the catheter shaft itself, taking up valuable space on the catheter shaft. The plurality of tracking coils may be used to create a linear vector for approximating the location of the electrode at the distal end of the catheter shaft. In other circumstances, the tracking devices may also be used to compute the curve of the shaft as an interpolated polynomial, such as a cubic spline. The computed curve may then be extrapolated to estimate the projected location of the electrode at the distal end of the catheter shaft. The location of the electrode at the distal end of the catheter shaft may thus be an indirectly computed estimate, not a directly measured value.
Thus, there remains a need for an apparatus and method for directly measuring the location of an electrode disposed on a catheter (e.g., the electrode disposed at the distal tip of a catheter) without having to resort to extrapolation or estimation. There also remains a need for a apparatus and method for providing information regarding the flex of a catheter without having to place multiple tracking devices on the catheter shaft itself.